Shading generator



Jan. 4, 1944. R, E, KEssLER 2,338,646

SHADING GENERATOR Filed Jan. l5, 1942 K flrmre/vEY Patented Jan. 4,1944v SHADING GENERATOR Robert E. Kessler, Upper Montclair, N. J.,assignor to Allen B. Du Mont Laboratories, Inc., Passaic, N. J., acorporation of DelawareA Application January 13, 1942, serial No. 26,56

1o claims.- -(ci. rvs- 7.2)

This invention relates to the generation and' It is picphasing of a highfrequency sine wave. particularly useful for shading a television ture.

By this invention a sine wave can be obtained and variedover a widerange of line scanning frequencies, without complicated circuitadjustments, for the purpose of shading television pictures in whichwidely different scanning frequencies are used.' This is accomplishedwithout the necessity of supplyinga special or separate synchronizingpulse to the shading generator. A sawtooth impulse is used for the inputforgcnerating the sine wave and the phase may be changed over theextraordinary wide range of 360 degrees.

one of the objects''f this invention is to obtain a sine wave that canbe used for shading a television picture over a wide range of scanningfrequencies where a flexible scanning system is employed. yIn carryingout the invention a sawtooth signal at the horizontal scanning rate anda sawtooth signal at the vertical scanning rate are converted into sinewaves and these sine Waves are used for shading an iconoscope. When thescanning rate is changed by-changing the frequency of the sawtoothsignal, the frequency of the sine wavefollows automatically over a wide'range of frequencies. 4

'I'he invention ,may be understood from the description in connectionwith the accompanying drawing, in which:

Fig. 1 is a block diagram showing ment of parts; and Fig. 2 is a circuitarrangement for. generating and shifting the phase of the sine wave usedfor shading.

As indicated in Fig. 1, a vertical synchronizing an arrangewill beobvious how the vertical synchronizing wave is also generated and phased"in asimilar manner. 'f

In Fig. 2l the horizontal synchronizing signal is applied across theresistor Rito the grid G of the vacuum tube V, the resistor R beingadjusted to supply the proper bias onthis grid. The condenser C1 andinductance L1, shunted by the resistor Ra, are adjusted to resonate theplate P of the tube; Vqso as to oscillate ai; the frequency of thesignal applied to the grid G. The resulting sine waves are caused tovappear through the the condenser C2 across the primary Ti of thetransformer. The secondary T. of this transformer is grounded asindicated, and is loaded with a series circuit containing the condenserC:

and variable resistor Ra. By varying the resistance Re the sine wavefrom the secondary Tr can be shifted over a phase angle of approximately180. The reversing switch` S between the transformer secondary Tr andthe load enables the phase angle to be shifted 180 so that the sine wavecan then be shifted 'along the other 180 of the 360 degrees. The Q ismade low so that broad tuning, say over an octave,iis possible.

Scanning frequencies can be obtained with this invention from 15,'750cycles per second for 525 line; v frametelevision pictures to 9,375cycles or any other circuit adjustmentsbeing necessary.'

per second for 625 line, 15 frame television picl tures, for shadingwithoutv any change in tuning Thisinvention is also useful for observinga television signal at'llne frequency on an oscillograph. While doingthis the sine-wave is used as a time base. When it is desired to observea remote television signal onA an oscillograph, the horizontalsynchronizing frequency sawtooth sigl nal of the television receiver isapplied to the ossawtooth signal is fed to the mixer tube I indiy fcated diagrammatically; a 60-cycle sine wave from a power line is fed tothe mixer tube 2; the same vertical synchronizing sawto'oth signal isfed to the parabola generator I, the output of which is fed to the mixerI; a horizontal synchronizing sawtooth signal is fed to the mixer l; thesame horizontal synchronizing sawtooth signal is fed to the parabolageneratori, the output of which is fed to the mixer l.; and the samehorizontal synchronizing sawtooth signal is fed to the sine-wavegenerator l, the output of which is fed to the mixer 8. The compositesignals are scope for shading the same.

led to the output tube I0 and thence to an icono- Fig. 2 shows how thehorizontal synchronizing cillator input to produce a sinel wave for usein the oscillograph. The tube V of Fig. 2 and its circuits constitute anoscillator for this purpose.

While the description above has 'set forth the details for converting asawtootlr wave over a range of horizontal scanning frequencies into asine wave of variable phase suitable for television shading purposes, ithas been found that input signals-of impulse shape and other wave formsat horizontal scanning frequencycan also be applied to the circuit ofFig.2 resulting in variable phase sine waves suitable for shading andsuitable for osciliograph sweep circuits. 1

vWhatisclaimedis: l l .y 1;- In a device for generating and phasing sinewaves from saw/toothv signals for shading television pictures, a vacuumtube with a biased grid to which the sawtooth signal is applied, aresonant circuit connected to the plate of said tube to causeoscillations at the frequency of the sawtooth signal, a transformer tothe primary of which said oscillations are applied, and a series circuitload on the secondary of said transformer.

2. vIn a device for generating and phasing sine Waves from sawtoothsignals for shading television pictures, a vacuum tube with a biasedgrid lto which the sawtooth signal is applied, a resonant circuitconnected to the plate of said tube to cause oscillations at thefrequency of the sawtooth signal, a transformer to the primary of whichsaid oscillations are applied, a series circuit load on the secondary ofsaid transformer, and a variable resistance in said last named circuit.i

3. In a device for generating and phasing sine waves from sawtoothsignals for shading television'pictures, a vacuum tube with a biasedgrid to which the sawtooth signal is applied, a resonant circuitconnected to the plate of said tube to cause oscillations at thefrequency of the sawtooth signal, a transformer to the primary of whichsaid oscillations are applied, a series circuit load on the secondary ofsaid transformer, and a reversing switch in said last named circuit.

4. In a device for generating and phasing sine waves from sawtoothsignals for shading television pictures. a vacuum tube with a biasedgrid to which the sawtooth signal is applied, a resonant circuitconnected to the plate of said tube to cause oscillations at thefrequency of the sawtooth signal, a transformer to the primary of whichsaid oscillations are applied, a series circuit load on the secondary ofsaid transformer,

quency of the sawtooth signal, a transformer to the primary of whichsaid oscillations are applied, and a series circuit load on thesecondary of said transformer.

6. In a device of the character described, means for producing fromaline frequency sawtooth signal a composite signal for line frequencyshading of television'pictures, said means comprising a sine wavegenerator and a parabola generator to which said sawtooth signal isapplied, and mixers for mixing the outputs therefrom for application toan iconoscope for shading purposes. 1

7. In a device of the character described, means for producing from aline frequency sawtooth signal a composite signal for line frequency Yshading of television pictures, said means cornand a gain controlconnected tothe output of prising a sine wave generator and a parabolagenerator to which said sawtooth signal is applied, and mixers formixing the outputs therefrom and said sawtooth signal for application toan iconoscope for shading purposes.

8. The device of claim 6, in which said sine Wave gener ator is adaptedto have its phase shifted over approximately 360 degrees.

9. In a device of the character described, means for producing from afield frequency sawtooth signal a composite signal for field frequencyshading of television pictures which comprises a parabola generator towhich said sawtooth signal is applied and mixers for mixing the outputfrom said parabola generator and said sawtooth signal for application toan iconoscope for shading purposes.

l0. In a device of the character described, means for producing from afield frequency sawtooth signal a composite signal for field frequencyshading of television pictures which comprises a parabola generator towhich said sawtooth signai is applied and mixers for mixing the outputfrom said parabola generator and said sawtooth signal and a sine wavefrom a power line for application to an iconoscope for shading purposes.

ROBERT E. KESSLER.

